CONCORD, N.H. — A Vermont man charged with killing a private school trustee at a New Hampshire hotel has signaled he will invoke a defense of not guilty by reason of insanity.

Lawyers for Rodney Hill of Danville, Vt. have requested a hearing on their notice of his intent to enter the insanity plea, court documents show.

Hill was indicted in June for second-degree manslaughter in the stabbing death of Catherine Houghton, 70, of California in the lobby of the Hampton Inn in Littleton Jan. 28.

Houghton, a 1960 graduate of the White Mountain School in Bethlehem, was in town for meetings of the school’s board of trustees. She had remained an extra day to rehearse with the school’s a cappella choir, school officials said.

Prosecutors say that Houghton and Hill, 37, did not know one another and the attack appears to have been random. Hill had checked into the hotel earlier in the day.

According to the autopsy report, Houghton died of a stab wound to the neck.

“Hill then began talking to Green about an apocalypse, that he was the salvation and stated something about smartphones,” according to the affidavit.

Hill told police his father was Lucifer, and blamed him for not being able to send an email response to his boss or make a phone call. “He believed his father, as the devil, would appear in a different form that he would not recognize,” the affidavit states.